The present invention relates to an antimicrobial cosmetic pigment, its production process, and a cosmetic composition containing it, and, more specifically, to an antimicrobial cosmetic pigment made by forming a layer of amorphous glassy coating over the surface of cosmetic pigment and intercalating antimicrobial metals inside the lattice structure of said coating layer.
The objective of adding preservative to cosmetic is to prevent cosmetic from deterioration and change of fragrance by microbes, and from germination of fungi by sterilizing or restraining the breeding of the microbes which may be originated from the raw material or may find duirng the process for production and filling of cosmetics, or while cosmetics are in use by consumers.
Preservatives used in manufacture of cosmetics include, as are found in the descriptions of Korean Specification for Raw Material of Cosmetics: formic acid; glutaric aldehyde; chlorohexiding gluconate and dihydrochlorate; dimethyloxazolidine; dimethoxane; dibromohexamidine and its salts; diazolidinyl urea; DMDM hydantoin; 2,4-dichlorobenzyl alcohol; 3,4-dichlorobenzyl alcohol; dihydroacetic acid and its salts; sodium lauroyl sarkocin; methenamine-3-chloroarylochloride; inorganic sulfide and hydrogen sulfides; benzyl alcohol; benzyl hemiformal; borax; 5-bromo-5-nitro-1,3-dioxane; 2-bromo-2-nitropropane-1,3-diol; bromoalkylisoquinolium; bromochlorophene; biphenyl-2-ol (O-phenylphenol)and its salts; 1,3-bis(hydromethyl)-5,5-dimethylimidazolidone-2,4-dione; salicylic acid and its salts; phenyl salicylate; sodium iodate; sorbic acid and its salts; zinc pyrithione; benzoic acid and its salts; alkyl (C.sub.12 .about.C.sub.22) trimethylammonium bromide and chloride; hydrochloric acid-alkyldiaminoethyl glycine solution (30%); chlorobenzetonium; chlorobenzalconium; undecylenic acid and its salts; monoethanolamide; imidazolidinyl urea; isopropyl methylphenol; isopropylcresol; thiram; captane; quarternium-15; quinoline-8-ol and its salts; a mixture of 5-chloro-2-methyl-isothiazole-3(2H)-one and 2-methylisozol-3 (2H)-one; chlorobutanol; chloroacetamide; p-chloro-m-cresol; chloroxylenol; chlorophenecine; chlorophene; 1-(4-chlorophenoxy)-1-(imidazole-1-yl)-3,3-dimethylbutane-2-one; tetrabromo-o-cresol; trixrosane; trichlorocarbyne; paraoxybenzoic acid ester; phenoxyethanol; phenoxyisopropanol; phenol; o-phenylphenol; formaldehyde and paraformaldehyde; poly(1-hexamethylenebiguanid hydrochloric acid); propionic acid and its salts; pyroctonolamine; pyridine-2-ol-1-oxide; hexamethylene tetraamine; hexetidine; hexamidine and its salts; N-(hydroxymethyl)-N-(dihydroxymethyl-1,3-dioxo-2,5-imidazolidinyl-4)-N'-hy droxymethyl) urea; 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2-pyridone and its monoethanol amine salt (promulgation No. 1993-57, by the Ministry of Health and Social Affairs).
But dichlorophene, mercury and its compounds, bithiol, salicylanilide halide, and the like are strictly forbidden from use because of their toxicity, despite their antiseptic bacteriocidal effects.
Generally, microbes including bacteria need water and nutrients to reproduce. In cosmetics many kinds of raw materials are used, and microbes can reproduce making use of the carbon source in them. But microbes cannot reproduce in products containing no water, even if they settle on them, yet they can possibly remain in the spore state. While products containing some antibacterial aromatics or ethanol can restrain reproduction of microbes, it is inevitable to use preservatives in emulsion types of cosmetics, skin conditioners, shampoos, make-up products, etc.
In other words, basically, cosmetics are emulsions of water, oil, surfactants, and particles, or are in the cake or powdery forms, and therefore, as in the case of food, are easily preyed upon by microbes, whereby deterioration, change of smells or colors, or the generation of fungi can not merely lower the commercial values of cosmetics but can badly affect the skin of users. Therefore, preservative ingredients are added in production of cosmetics to sterilize the harmful microbes on human skin, thereby preventing dermatic troubles arising from microbes.
But only a limited amount of such preservatives can be used in a cosmetic because of their possible pernicious effects upon the bodily safety of users. For instance, of the preservatives listed in the promulgation of the Ministry of Health and Social Affairs, DMDM hydantoin is allowed only by 2.0 wt % (in preparations for hair), benzoic acid and its salts by 0.5 wt %, and paraoxybenzoic acid ester by 1.0 wt % only.
On the one hand, the factors to influence the preservative effects of preservatives mixed in cosmetics include the pH of cosmetics, solubility of preservatives, joint use with other preservatives, nonionic surfactants, powders, electrolytes, humectants, raw material of containers, etc. For instance, paraoxybenzoic acid ester exercises normal antimicrobial activity when the pH is neutral or acidic, but this activity decreases if pH is alkaline, and in the case of products which contain water soluble polymers or nonionic surfactants its preservative or antimicrobial activity decreases because these ingredients can adsorb the paraoxybenzoic acid ester or form complex compounds decreasing its concentration considerably, and, not only that, there are cases when the powders mixed in the product or the containers of different raw materials, adsorbing the preservative, decrease the preservative or antimicrobial activity.
Then conventional preservatives have problems due to limitations in the quantity for mixing for fear of their own irritations; the pH effects of cosmetic compositions; their own solubility; effects from combined use with other preservatives; decrease of antimicrobial activity due to the adsorption of the used nonionic surfactants and water soluble polymers; effects of electrolytes and humectants; use of larger quantities of preservatives actually mixed due to the adsorption of the powders or containers than otherwise required; maintenance of lasting antiseptic or antimicrobial activity; and insurance of safety.
Now in other fields than production of cosmetics, too, antiseptic materials other than the above have been in use in production of antiseptic fibers, sterilization of soil, or improvement of the quality of water. Namely, for raw materials which made use of metals with antimicrobial effects, alkali metal carbonate and zeolite (Japanese Patent Laid-Open No. sho 60-100504), antimicrobial fiber products (Japanese Patents Laid-Open Nos. hei 2-307968 and 3-124810), ion-exchanged titanium oxide (Japanese Patent Laid-Open No. hei 3-52804), silicate (Japanese Patent Laid-Open No. hei 3-193707), sepiolite (Japanese Patent Laid-Open No. hei 3-275605), carbon (Korean Patent Publication No. 90-3582), heavy metal salt of hyaluronic acid (International Patent Application No. WO 87-05517) are known to have been used as antimicrobial agents.
But such antimicrobial materials are usually ion-exchanged for carrying of metals, and for this purpose they are often made porous to raise the ion-exchange rate, the surface areas getting large. In consequence they are rough and stiff to the feel for cosmetic pigments, and also due to the high oil-absorption, and the fear of stimulation for oxidation at contact with oils, they are subject to limitation in use, that is, in short, they are inadequate for cosmetics, having problems in other aspects also such as short maintenance of the antimicrobial effects, loss of activity due to adsorption of other adsorption materials, etc.